Let me take a crack at this - first thing you need to do is take a hard look at parks you want to, or are considering visiting and see what the limitations are on size. Also, how many locations the NP has for class A type vehicles and hookups. Example - Yellowstone only has one CG with hookups and space to really handle large class A's and that is at Fishing Bridge. Most NF campgrounds restrict size to 29', max, but you will always see bigger units crammed in tight spaces. Most NP's have dry camping sites available, but again, size becomes the listing factor. Same goes for RMNP - you just really have to research what your options are. If you really require a large Class A, then you are really going to be limited, I think, in most NP's. This is one of the reasons we opted for a Class C Sprinter pulling a Jeep JK. No issue wherever we go space wise for size.